Precise unzipping of flattened carbon nanotubes to regular graphene nanoribbons by acid cutting along the folded edges

Abstract

Precise unzipping of carbon nanotubes (CNTs) is achieved using flattened carbon nanotubes (F-CNTs) as the starting material and using acid to cut along the folded edges, as these high energy sites are preferentially attacked to yield regular graphene nanoribbons (GNRs). All-bilayer GNRs with narrow uniform width (8–12 nm) and straight edges are fabricated by unzipping flattened double-wall CNTs (F-DWCNTs) using mixed acids of H2SO4 and KMnO4. Transmission electronic microscopy observations confirm the localized and directional unzipping of the F-DWCNTs and the formation of regular bilayer GNRs. The oxidation temperature and acid concentration control the degree of oxidation, the extent of unzipping, and the exfoliation of F-DWCNTs from their bundles. Under certain conditions, assemblies of interconnected GNRs are formed by unzipping F-DWCNT bundles and partial exfoliation. The precise unzipping of flattened CNTs provides a reliable and scalable process for fabricating regular GNRs with controlled structures and morphologies, as demanded for applications that use them as structural, functional and electronic materials.